how big are the decay ticks on a small magical chest?

[JakeRivers 2,921]

Since I got my small magical chest the decay tics are far apart but when they happen its been around 12 each time, is this normal on these?

 

I was under the impression they should last a few years, but at this rate its going to be gone a lot sooner than I was expecting, it is now up to 56 damage.

 

 

[Wurmhole 3,650]

I bought a used one a few years ago. Has a lot less damage than yours now. Something is wrong with yours it seems. Mine sits in my cart all the time.

[Explora 569]

Magic chest is locked and inside a HotA statue "with re-heated beans" inside an underground house "Mad Nad's microwaved potatoes" underneath The Old Contemptibles deed.

Edited August 19, 2017 by Explora
adding more info